so far just Max+Max2
There are a few that I have my eye on and - when I have more free time - I might get. Whilst there are some others that I currently own that I have not used/tried with vista yet and so might warrent getting again due to compatabilty problems.

So far:
Disciples.
Fallout 1.
Fallout 2.
Fallout Tactics.
The Freespace series will probably be my next buy, but reality is getting in the way of my gaming a lot these days.

Original War, Shogo, Redneck Rampage, Fallout 2, Giants, MDK 2, Die by the sword.
I want to buy Disciples or Fallout Tactics next - well, in case nothing better comes out.
Yours too? I hate that guy!

Six.

Five,
Fallout 1, 2, Tactics.
Redneck Rampage
Giants: Citizen Kabuto

fallout 1
Fallout Tactics
hostile waters
Descent 1 and 2
Sacred
It is "really" easy to buy games at these prices, especially with the NO drm and additions they have with them.

So far I own six.
Fallout 1, 2, Tactics
Freespace 1, 2
Collin Mcrae Rally 2005
The next two that I plan to purchase will be Gothic and Sacred Gold, unless something else is released that I desire more.

Shogo
Freespace 2 (the free one)
MAX series
Sacrifice
Hostile Waters
Operation Flashpoint
Sensible Soccer
So a grand total of 7 games; Or another way to look at it is $40, which is less then the price of one current release title.

How do people get these free games? Do GOG sometimes just throw in a virtual coupon with a sale, or what?

I think it was something like "buy your 1st one, get 1 for free" during early beta. I must have joined a bit too late though ^^

Yeah, when I first joined (back near the beginning of the closed beta) there was a buy one get one free offer on interplay games.

Sensible Soccer 2006

0 so far, but planning on Gothic right after I finish playing Fallout3. Unfortunately I have the disks for FAllout 1, 2 and Freespace 1 and 2, otherwise I would have bought those as well.

Original War
FreeSpace
Castles 1 & 2 (Don't really care for)
Sacrifice
I'm planning on grabbing:
Freespace 2
Fallout Tactics (maybe)
and probably Gothic.

I have bought four so far.
Soilders : Heros of WW2
Lionheart : Legacy of the Crusader
Original War
Sacred Gold
I plan on buying many more...most likely after Christmas.